Search for Oxide Hyperferroelectrics

Ferroelectric materials are used in a variety of FE-RAM devices, but the ferroelectric components are still far from optimal under the size constraints desired to enable future scaling. Upon miniaturization, the magnitude of the polarization decreases (or even vanishes) and the coercive fields often increase in ferroelectric oxides. Recently, hyperferroelectric materials have appeared as a potential solution to this issue, as they permit few atomic layers of the ferroelectric material to exhibit high spontaneous polarization at the nanoscale. However, hyperferroelectrics remain a rare subclass of proper ferroelectrics, with fewer than 15 compounds identified to date. In this work, we explore the stability and physical properties of candidate hyperferroelectric oxides in the niobate family using density functional theory (DFT) simulations. For these compounds, we examine the variation of unstable longitudinal and transverse optic modes with respect to macroscopic physical properties (e.g., the bandgap, dielectric constant, polarization, critical thickness, etc.) to better understand the physical features supporting hyperferroelectricity, enabling the design of next-generation materials.